Field of the Invention
The invention relates to a lens driving device, and in particular to a lens driving device which requires less focusing time.
Description of the Related Art
Many mobile devices such as mobile phones are equipped with digital cameras as a basic requirement nowadays, and this is only possible thanks to the miniaturization of lens driving devices. In order to provide automatic focusing or zooming, a commonly used miniature lens driving device is a Voice Coil Motor (VCM), which carries a lens and can move the lens back and forth along an image-capturing optical axis by means of a coil, a magnet, and a spring sheet.
Generally, when a lens (of VCM) is moved to a fixed position to bring the subject into focus, it may shake for a period, and then is slowly reaches a steady state. This time required (for the lens) to move to the stop from being at rest is called the Dynamic Response Time, which affects the length of the focusing time of the lens driving device (The longer the Dynamic Response Time, the longer the focusing time. This adversely affects the effectiveness of the lens driving device). Therefore, how to shorten the Dynamic Response Time to reduce the focusing time of the lens driving device deserves careful consideration.